Pulsed laser anneal process for transistor with partial melt of a raised source-drain

ABSTRACT

A non-planar transistor including partially melted raised semiconductor source/drains disposed on opposite ends of a semiconductor fin with the gate stack disposed there between. The raised semiconductor source/drains comprise a super-activated dopant region above a melt depth and an activated dopant region below the melt depth. The super-activated dopant region has a higher activated dopant concentration than the activated dopant region and/or has an activated dopant concentration that is constant throughout the melt region. A fin is formed on a substrate and a semiconductor material or a semiconductor material stack is deposited on regions of the fin disposed on opposite sides of a channel region to form raised source/drains. A pulsed laser anneal is performed to melt only a portion of the deposited semiconductor material above a melt depth.

This is a Continuation of application Ser. No. 14/667,544 filed Mar. 24,2015 which is a Divisional of application Ser. No. 13/976,822 filed Jun.27, 2013 now U.S. Pat. No. 9,006,069 issued Apr. 14, 2015, which is aU.S. National Phase application under 35 U.S.C. § 371 of InternationalApplication No. PCT/US2011/065910, filed Dec. 19, 2011.

TECHNICAL FIELD

Embodiments of the present invention relate to transistors and moreparticularly relate to laser annealing of a raised source and/or araised drain of a transistor.

BACKGROUND

While laser “melt” anneal processes for transistor source and/or drain(i.e., source/drain) formation are known, they are not typical in highvolume logic device manufacturing. One forecasted application for apulsed laser anneal process is to melt semiconductor material in thesource/drain. The melt advantageously increases the activation ofdopants relative to other forms of anneal where the semiconductor is notmelted, thereby improving transistor parametrics, such as externalresistance (R_(ext)), specific contact resistance (R_(c)), etc. The meltis possible in a planar architectures in part because for a crystallinesemiconductor substrate, or perhaps an insulating field dielectricsurrounds the sides of the source/drain, forming a “bowl” capable ofcontaining the melt.

For non-planar architectures, for example where a semiconductor finstructure is formed, the source/drain is typically elevated from thesurroundings such that a laser melt anneal can cause a raisedsource/drain to flow, losing its desired shape, structural relationshipto, and/or electrical continuity with, the channel region of thetransistor.

Non-planar architectures benefiting from the higher source/drain dopantactivation possible through laser anneal and techniques for performingsuch laser anneals are therefore advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, and can be more fully understood withreference to the following detailed description when considered inconnection with the figures in which:

FIG. 1A is a cross-sectional isometric illustration of a non-planartransistor with a raised source and drain, in accordance with anembodiment;

FIG. 1B is a cross-sectional isometric illustration of a non-planartransistor with a raised source and drain, in accordance with anembodiment;

FIGS. 2A, 2B and 2C are cross-sectional illustrations of a raisedsource/drain in accordance with embodiments;

FIG. 3 is a dopant profile of a raised source/drain, in accordance withan embodiment;

FIG. 4 is a flow diagram illustrating a method of fabricating anon-planar transistor with a raised source and drain, in accordance withan embodiment;

FIG. 5 is a flow diagram illustrating methods of laser annealing only aportion of a raised source/drain, in accordance with embodiments;

FIGS. 6A, 6B, 6C, 6D, 6E, 6F are flow diagrams illustrating methods oflaser annealing only a portion of a semiconductor layer in a raisedsource/drain, in accordance with embodiments;

FIGS. 7A, 7B, and 7C are flow diagrams illustrating methods of laserannealing fewer than all semiconductor layers of a semiconductor stackin a raised source/drain, in accordance with embodiments; and

FIG. 8 is a functional block diagram of a mobile computing system inwhich the non-planar transistors described herein are employed, inaccordance with embodiments.

DETAILED DESCRIPTION

In the following description, numerous details are set forth, however,it will be apparent to one skilled in the art, that the presentinvention may be practiced without these specific details. In someinstances, well-known methods and devices are shown in block diagramform, rather than in detail, to avoid obscuring the present invention.Reference throughout this specification to “an embodiment” means that aparticular feature, structure, function, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrase “in an embodiment” invarious places throughout this specification are not necessarilyreferring to the same embodiment of the invention. Furthermore, theparticular features, structures, functions, or characteristics may becombined in any suitable manner in one or more embodiments. For example,a first embodiment may be combined with a second embodiment anywhere thetwo embodiments are not mutually exclusive.

The terms “coupled” and “connected,” along with their derivatives, maybe used herein to describe structural relationships between components.It should be understood that these terms are not intended as synonymsfor each other. Rather, in particular embodiments, “connected” may beused to indicate that two or more elements are in direct physical orelectrical contact with each other. “Coupled” my be used to indicatedthat two or more elements are in either direct or indirect (with otherintervening elements between them) physical or electrical contact witheach other, and/or that the two or more elements co-operate or interactwith each other (e.g., as in a cause an effect relationship).

The terms “over,” “under,” “between,” and “on” as used herein refer to arelative position of one material layer with respect to other layers. Assuch, for example, one layer disposed over or under another layer may bedirectly in contact with the other layer or may have one or moreintervening layers. Moreover, one layer disposed between two layers maybe directly in contact with the two layers or may have one or moreintervening layers. In contrast, a first layer “on” a second layer is indirect contact with that second layer.

Described herein are non-planar transistor embodiments includingpartially melted raised semiconductor source/drains disposed on oppositeends of a semiconductor fin with the gate stack disposed there between.The raised semiconductor source/drains comprise a super-activated dopantregion above a melt depth and an activated dopant region below the meltdepth. The super-activated dopant region has a higher activated dopantconcentration than that of the activated dopant region and/or has anactivated dopant concentration that is constant throughout the meltregion. Methods of fabrication include forming a fin on a substrate anddepositing a semiconductor material or a semiconductor material stack onregions of the fin disposed on opposite sides of a channel region toform raised source/drains. A pulsed laser anneal is performed to meltonly a portion of the deposited semiconductor material above a meltdepth. The super-activated region, as contained to a melt depth thatcorresponds to less than an entirety of the raised source/drain limitsthe loss of raised source/drain semiconductor material integrity. Evenwith less than all of the raised source/drain region melted by the laseranneal, it has been found that in embodiments, the super-activatedregion formed above the melt depth improves transistor parametrics, forexample R_(c), relative to a raised source/drain having onlyconventional dopant activation.

Embodiments of the present invention may be applied to planar ornon-planar MOS-FETs (i.e., finFETs) which have a raised source/drain.For example, devices with a three-dimensional architecture, such astri-gate or multi-gate devices may utilize the attributes and techniquesdescribed herein. FIG. 1A is a cross-sectional isometric illustration ofa non-planar (tri-gate) transistor 100 with a raised source and drain,in accordance with an embodiment. The transistor 100 is disposed on abulk-substrate 101, which may be any conventional material, such as, butnot limited to single crystalline silicon, germanium, III-V compoundsemiconductor (e.g., GaAs, InP, etc.), III-Nitride compoundsemiconductor (e.g., GaN), or sapphire. In alternate embodiments,semiconductor on insulator (SOI) substrates are utilized, as known inthe art.

The non-planar transistor 100 includes a semiconductor fin 103 (e.g.consisting essentially of monocrystalline silicon), having opposingsidewalls 103A, 103B and a top surface 103C. Adjacent to a portion ofthe fin sidewalls 103A, 103B is a field isolation dielectric 102 (e.g.,silicon dioxide). A gate electrode stack 106 is formed around at leastthe sidewalls 103A, 103B of the fin 103 to form a semiconducting channelregion 204 (depicted in FIG. 1B).

A source/drain 110A is disposed at opposite ends of the fin 103, oneither side of the gate electrode stack 106 as separated by anintervening pair of gate isolation spacers 114. The source/drain 110A is“raised” from the fin 103 by at least one semiconductor material that isdeposited on one or more surfaces of the fin 103. In FIG. 1A, the raisedsource/drain includes a dopant activated semiconductor material 120Adeposited on each of the opposite fin sidewalls 103A, 103B as well asthe top fin surface 103C. FIG. 1B is an isometric illustration of anon-planar transistor 200 with a raised source/drain 110B, in accordancewith another embodiment where the raised source/drain includes anactivated first semiconductor material 140 deposited on only the top finsurface 103C because the semiconductor fin 103 is recessed below thefield isolation dielectric 102.

Returning to FIG. 1A, in embodiments, raised source/drain 110A consistsessentially of a homogenous semiconductor material. In one suchembodiment, the raised source/drain 110A consists essentially of silicon(e.g., same as the fin 103) or consists essentially of asilicon-germanium (SiGe) alloy, or any other known compoundsemiconductor. The raised source/drain 110A includes electricallyactivated dopants (e.g., n-type for an NMOS device and p-type for a PMOSdevice). The portions of the fin 103 disposed below the raisedsource/drain 110A also includes electrically activated dopants in theexemplary embodiment.

For embodiments illustrated by FIG. 1A, although the raised source/drain110A is of a homogenous semiconductor material, activated dopantconcentration is distinguished between the activated semiconductormaterial 120A disposed below a melt depth 115B and a super-activatedsemiconductor material 125 disposed above the melt depth 115B. The meltdepth 115B therefore represents the interface within the raisedsource/drain 110A between deposited semiconductor material that has beenlaser annealed and therefore super-active and deposited semiconductormaterial that has not been laser anneal and therefore active, but notsuper-active. The melt depth 115B may vary so that the relativeproportion of the raised source/drain comprising the super-activatedsemiconductor material 125 may vary. However, in the exemplaryembodiment the melt depth 115B does not coincide with any point on asurface of the fin 103. As such, with the melt depth 115B not contactthe fin 103, the super-activated semiconductor material 125 is containedentirely within deposited semiconductor material that is the raisedsource/drain 110A.

FIG. 3 is a line plot representing an activated dopant profile (e.g.,cm⁻³) of a raised source/drain as a function of depth into a raisedsource/drain, in accordance with an embodiment. Generally, FIG. 3 isrepresentative of a depth profile taken at any incident milling angleinto the raised source/drain 110A, although absolute depths and dopantconcentrations can be expected to vary based on the technique employedfor doping the raised source/drain 110A and on the milling path, etc. Asshown, above the demarcation 315B, corresponding with the melt depth115B, there is an abrupt, box-like dopant profile 325 that issubstantially constant throughout the thickness of the super-activatedsemiconductor material 125. The activated dopant concentration is not afunction of depth within the super-activated semiconductor material 125because of the equilibrium achieved through a laser melt anneal. At thedemarcation 315B, there is a discontinuity in the dopant profile wherethe box-like dopant profile 325 meets a conventional solid statediffusion limited dopant profile 320A within the activated semiconductormaterial 120A. As illustrated, within the activated semiconductormaterial 120A, the dopant profile is a function of the depth within theraised source/drain. In the exemplary embodiment, the concentration ofactivated dopants is also higher within the super-activatedsemiconductor material 125 than it is within the activate semiconductormaterial 120A.

In embodiments, a raised source/drain includes a deposited semiconductorstack of two or more distinct semiconductor materials. In embodiments,the distinct semiconductor materials are utilized, at least in part, todifferentiate the melting temperature within the raised source/drain.Generally, a lowest melting temperature semiconductor is to be a toplayer of the deposited semiconductor stack and a highest meltingtemperature semiconductor is to be a bottom layer of the depositedsemiconductor stack to ensure a melt of the lowest melting temperaturesemiconductor is contained within the raised source/drain 110A by thehighest melting temperature semiconductor.

FIG. 1B illustrates an exemplary embodiment where the raisedsource/drain 110B includes the activated first semiconductor material140 and the super-activated second semiconductor material 150B where thefirst and second semiconductor materials are distinct such that thesecond semiconductor material has a lower melting temperature than thefirst semiconductor material. Generally, the semiconductor materialsselected for the first and second semiconductor materials may be anythat have sufficient difference in melting temperature to accommodatethe goal of limiting the melt depth to somewhere above the fin surface(e.g., 103C in FIG. 1B). In one exemplary embodiment, the activatedfirst semiconductor material 140 consists essentially of silicon whilethe super-activated second semiconductor material 150B consistsessentially of GaAs. In another exemplary embodiment, the activatedfirst semiconductor material 140 consists essentially of InP while thesuper-activated second semiconductor material 150B consists essentiallyof GaP. In another exemplary embodiment, the activated firstsemiconductor material 140 consists essentially of silicon while thesuper-activated second semiconductor material 150B consists essentiallyof a SiGe alloy.

The melt depth 115B has a morphology dependent on the method employed tocontrol the laser melt anneal to some portion of a raised source/drain.FIGS. 2A, 2B and 2C are cross-sectional illustrations of a raisedsource/drain in accordance with embodiments. In the exemplaryillustrations, the cross-section is through a source/drain along thea-a′ plane substantially as illustrated in FIGS. 1A and 1B. In theembodiments corresponding to FIGS. 2A and 2B, a pre-amorphizationimplant sets the melt depth 115B within a homogenous depositedsemiconductor material.

In FIG. 2A, where a conformal plasma 230B is utilized for thepre-amorphization implant, amorphizing species (e.g., silicon,germanium, xenon, etc.) are conformally implanted to an amorphizationdepth 115A that is substantially conformal to an outer surface of theraised source drain region. As shown in FIG. 2A, the amorphized region120B forms a shell of substantially constant thickness (i.e., within10%). In the exemplary embodiment, the pre-amorphization implantconditions are such that the amorphization depth 115A does not contactthe semiconductor fin 103 (i.e., not all of activated semiconductormaterial 120A is amorphized). Notably, the conformality of the plasmaimplant enables the amorphized region 120B to contact the fieldisolation dielectric 102 which may advantageous reduce contactresistance where a contact metal will subsequently wrap around theraised source/drain and also contact the field isolation dielectric 102.As further illustrated by FIG. 2A, following the pulsed laser anneal(hv), the amorphized region 120B becomes the super-activatedsemiconductor material 125 with the melt depth 115B following theamorphization depth 115A.

In FIG. 2B, where a beamline pre-amorphization implant 230A is utilized,a non-conformal amorphized region 120B forms a cap of substantiallyconstant depth or thickness where the implant is symmetric relative tothe exterior surface of the raised source/drain. Alternatively where theimplant conditions are asymmetric (e.g., with a high angle ofincidence), the amorphized region 120B may be of varying depth orthickness. Notably, the non conformality of the beamline implantconfines the amorphized region 120B off the field isolation dielectric102. As further shown in FIG. 2B, following the pulsed laser anneal(hv), the amorphized region 120B again becomes the super-activatedsemiconductor material 125 with the melt depth 115B following theamorphization depth 115A.

In the embodiments corresponding to FIG. 2C, a differential compositionin the as-deposited semiconductor layers sets the melt depth 115B. Forsuch embodiments, epitaxial growth processes are utilized to set themelt depth 115B with growth conditions defining the morphology of theinterface between the first semiconductor material 140 and the secondsemiconductor material 150A, which upon melting becomes thesuper-activated semiconductor second semiconductor material 150B.Furthermore, in embodiments etching of the first semiconductor material140 prior to deposition of the second semiconductor material 150A mayprovide further control over the subsequent melt.

FIG. 4 is a flow diagram illustrating a method 400 of fabricating anon-planar transistor with a raised source and drain, in accordance withan embodiment. Method 400 begins with receiving a substrate, such as asilicon or SOI wafer as described elsewhere herein. At operation 410 afin is formed on the substrate. Any conventional technique known in theart may be employed at operation 410 to form the fin. For example, twoshallow trench isolation (STI) regions may be formed and then the STIregions recessed to exposed a fin disposed there between. In anotherexemplary embodiment, a portion of a silicon layer in an SOI wafer ismasked to form the fin. Also at operation 410, a gate stack (sacrificialor permanent) may be formed over a channel region of the fin (e.g., gatestack 106 in FIGS. 1A, 1B).

At operation 415, semiconductor material is deposited on the fin to formraised source/drain regions on opposite sides of a channel region in thefin. Any known technique for depositing semiconductor material suitablefor the purpose of forming a raised source/drain may be utilized atoperation 415. In one exemplary embodiment, a selective chemical vapordeposition (CVD) or molecular beam epitaxy (MBE) process is utilized todeposit polycrystalline semiconductor material over the exposed finsurfaces. In another exemplary embodiment, the CVD or MBE process formsa crystalline semiconductor material over the exposed fin surfaces withthe semiconductor material having the same crystallinity (e.g.,monocrystalline and having same crystallographic orientation) as thefin.

At operation 430, a laser anneal is performed to melt only a portion ofthe deposited semiconductor material of the raised source/drain that isabove a melt depth. Any known laser anneal process known to be suitablefor source/drain activation may be employed. In one embodiment, a pulsedlaser of a conventional wavelength, fluence, and pulse frequency isemployed. Following operation 430, the transistor is completed atoperation 450 through standard practices of the art.

FIG. 5 is a flow diagram illustrating a method 500 of laser annealingonly a portion of a raised source/drain, in accordance with embodiments.The method 500 begins with the operations 401 and 410, as describedelsewhere herein. Following operation 410, in one embodiment the method500 proceeds to operation 415A where a single semiconductor material isdeposited on the fin to form a raised S/D region (or at least wheremultiple semiconductor materials are deposited, the difference incomposition does not provide a significant difference in meltingtemperature). For this embodiment, at operation 540 a preamorphizingimplant is performed to amorphize a portion of the depositedsemiconductor material to an implant depth (e.g., as illustrated inFIGS. 2A, 2B). Depending on the embodiment, the pre-amorphizing implantmay be any of a beamline ion implantation, an angled implantation, or aconformal plasma implantation. Following the pre-amorphizing implant,the laser melt operation 542 is performed substantially as describedelsewhere herein, melting only the pre-amorphized portion of thesemiconductor material deposited at operation 415A.

In another embodiment, method 500 proceeds from operation 410 tooperation 415B where a semiconductor material stack is deposited on thefin to form a raised source/drain. In one embodiment of operation 415B,a first semiconductor material is deposited on the fin and then a secondsemiconductor material of differing composition is deposited over thefirst semiconductor material. The melting temperature of the firstsemiconductor material is higher than that of the second semiconductormaterial (e.g., at least 100° C., and preferably 200° C. or more).Subsequent to operation 415B, a laser anneal is performed at operation543 to melt the top deposited semiconductor material without melting theunderlying first semiconductor material. The method 500 then completesat operation 450, as previously described.

FIGS. 6A, 6B, 6C, 6D, 6E, 6F are flow diagrams illustrating methods oflaser annealing only a portion of a semiconductor layer in a raisedsource/drain, in accordance with embodiments wherein the raisedsource/drain includes a single semiconductor material of substantiallyhomogenous melting temperature.

FIG. 6A illustrates a first embodiment where method 601 begins atoperation 415A with depositing a single semiconductor material (e.g.,silicon, germanium, SiGe, GaAs, GaP, etc.) on a fin to form a raisedsource/drain. At operation 660, a source/drain implant is performedusing any conventional source/drain implant technique in the art. Forexample, in an NMOS transistor, an N-type dopant, such as phosphorus orarsenic may be implanted at operation 660. Or, in a PMOS transistor, anP-type dopant, such as boron may be implanted at operation 660. Atoperation 665, an activation anneal is performed to electricallyactivate dopants within the raised source/drain region (e.g., thoseimplanted at operation 660). In embodiments, the activation anneal is atleast one of a furnace thermal anneal, a rapid thermal anneal, amicrowave anneal, a flash anneal, or a sub-melt laser anneal whereconventional temperatures and anneal times are such that the raisedsource/drain is not melted. The pre-amorphizing implant is thenperformed at operation 540, substantially as described elsewhere herein.A pulsed laser anneal melting only the pre-amorphized portion of thedeposited semiconductor material is then performed at operation 542, asdescribed elsewhere herein. Following operation 542, the raisedsource/drain includes a super-activated semiconductor material disposedover an activated semiconductor layer.

FIG. 6B illustrates a second embodiment where method 602 begins atoperation 415A with depositing a single semiconductor material (e.g.,silicon, germanium, SiGe, GaAs, GaP, etc.) on a fin to form a raisedsource/drain. At operation 660, a source/drain implant is performedusing any conventional source/drain implant technique of the art. Forexample, in an NMOS transistor, an N-type dopant, such as phosphorus orarsenic may be implanted at operation 660. Or, in a PMOS transistor, anP-type dopant, such as boron may be implanted at operation 660. Atoperation 665, an activation anneal is performed to electricallyactivate dopants within the raised source/drain region (e.g., thoseimplanted at operation 660). The pre-amorphizing implant is thenperformed at operation 540, substantially as described elsewhere herein.Subsequently, a supplemental implant is performed at operation 667. Thesupplemental implant or co-implant may be of a same or different speciesas that implanted during the source/drain implant operation 660. Thesupplemental implant may serve to increase dopant concentrations withina portion of the activated raised source/drain. Following thesupplemental implant operation 667, a pulsed laser anneal melting onlythe pre-amorphized portion of the deposited semiconductor material isthen performed at operation 542, as described elsewhere herein.Following operation 542, the raised source/drain includes asuper-activated semiconductor material disposed over an activatedsemiconductor layer.

FIG. 6C illustrates a third embodiment where method 603 begins atoperation 670 with depositing a single semiconductor material (e.g.,silicon, germanium, SiGe, GaAs, GaP, etc.) that is in-situ doped on afin to form a raised source/drain. Any CVD feed gas known in the art tobe useful as a source for dopants during CVD of the semiconductor may beutilized at operation 670. In the exemplary embodiment, the method 603proceeds to the activation anneal operation 665. The activation annealis performed to electrically activate the in-situ deposited dopantswithin the raised source/drain region. However, depending on thedeposition process, the in-situ deposited dopants may already beelectrically activated in which case the activation anneal operation 665is not employed. Being optional, the activation anneal operation 665 isillustrated in FIG. 6C by a dashed box. The pre-amorphizing implant isthen performed at operation 540, substantially as described elsewhereherein. A pulsed laser anneal melting only the pre-amorphized portion ofthe deposited semiconductor material is then performed at operation 542,as described elsewhere herein. Following operation 542, the raisedsource/drain includes a super-activated semiconductor material disposedover an activated semiconductor layer.

FIG. 6D illustrates a fourth embodiment where method 604 begins atoperation 670 with depositing a single semiconductor material (e.g.,silicon, germanium, SiGe, GaAs, GaP, etc.) that is in-situ doped on afin to form a raised source/drain. Even though in-situ doped, the method604 proceeds to operation 660 where a source/drain implant is performed,as describe elsewhere herein. The source/drain implant operation 660supplements the source/drain dopants to enhance dopant concentrationbeyond that possible in-situ. The method 604 then proceeds to theactivation anneal operation 665, which is necessary in the exemplaryembodiment to activate the source/drain dopants implanted at operation660. Following activation anneal, the pre-amorphizing implant is thenperformed at operation 540, substantially as described elsewhere herein.A pulsed laser anneal melting only the pre-amorphized portion of thedeposited semiconductor material is then performed at operation 542, asdescribed elsewhere herein. Following operation 542, the raisedsource/drain includes a super-activated semiconductor material disposedover an activated semiconductor layer.

FIG. 6E illustrates a fifth embodiment where method 605 beings atoperation 670 with depositing a single semiconductor material (e.g.,silicon, germanium, SiGe, GaAs, GaP, etc.) that is in-situ doped on afin to form a raised source/drain. In the exemplary embodiment, themethod 605 proceeds to the optional activation anneal operation 665.Following activation anneal, the pre-amorphizing implant is thenperformed at operation 540, substantially as described elsewhere hereinand then the supplemental implant operation 667 is performed. Thesupplemental implant may serve to increase dopant concentrations withina portion of the activated raised source/drain. Following thesupplemental implant operation 667, a pulsed laser anneal melting onlythe pre-amorphized portion of the deposited semiconductor material isthen performed at operation 542, as described elsewhere herein.Following operation 542, the raised source/drain includes asuper-activated semiconductor material disposed over an activatedsemiconductor layer and the supplemental doping is confined to themelted region.

FIG. 6F illustrates a sixth embodiment where method 606 begins atoperation 670 with depositing a single semiconductor material (e.g.,silicon, germanium, SiGe, GaAs, GaP, etc.) that is in-situ doped on afin to form a raised source/drain. Even though in-situ doped, the method606 proceeds to operation 660 where a source/drain implant is performed,as describe elsewhere herein. The source/drain implant operation 660supplements the source/drain dopants to enhance dopant concentrationbeyond that possible in-situ. The method 606 then proceeds to theactivation anneal operation 665, which is in the exemplary embodiment toactivate the source/drain dopants implanted at operation 660. Followingactivation anneal, the pre-amorphizing implant is then performed atoperation 540, substantially as described elsewhere herein. At operation667, a supplemental implant is performed to further enhance dopantconcentration and/or implant a second species distinct from at least oneof the in-situ deposited species and the species implanted at operation660. A pulsed laser anneal melting only the pre-amorphized portion ofthe deposited semiconductor material is then performed at operation 542,as described elsewhere herein. Following operation 542, the raisedsource/drain includes a super-activated semiconductor material disposedover an activated semiconductor layer, again with the supplementaldoping confined to the melted region. As such, method 606 may beconsidered a combination of method 604 and method 605.

FIGS. 7A, 7B, and 7C are flow diagrams illustrating methods of laserannealing fewer than all semiconductor layers of a semiconductor stackin a raised source/drain, in accordance with embodiments.

In FIG. 7A, the method 701 begins with depositing a semiconductormaterial stack on a fin to form the raised source/drain at operation415B, as described elsewhere herein. In one exemplary embodiment, asilicon layer is first deposited followed by a GaAs layer. In anotherexemplary embodiment, a silicon layer is first deposited followed by aSiGe layer. In another exemplary embodiment, an InP layer is firstdeposited followed by a GaP layer. In the exemplary embodiment, themethod 701 proceeds to the activation anneal operation 665. Theactivation anneal is performed to electrically activate any in-situdeposited dopants within the raised source/drain region. However,depending on the deposition process at operation 415B, the in-situdeposited dopants may already be electrically activated in which casethe activation anneal operation 665 is not employed. At operation 543, apulsed laser anneal is performed to melt a top layer(s) of the depositedsemiconductor stack without melting all layers of the stack (e.g.,without melting a bottom semiconductor layer). In one exemplaryembodiment, a GaAs layer is melted while an underlying silicon layerremains unmelted. In another exemplary embodiment, a SiGe layer ismelted while an underlying silicon layer remains unmelted. In anotherexemplary embodiment, a GaP layer is melted while an underlying InPlayer remains unmelted.

In FIG. 7B, the method 702 begins with depositing a semiconductormaterial stack on a fin to form the raised source/drain at operation415B, as described for method 701. The method 702 proceeds to operation660 where a source/drain implant is performed, as describe elsewhereherein. The source/drain implant operation 660 supplements thesource/drain dopants to enhance dopant concentration beyond thatpossible during the stack deposition at operation 415B. The method 702then proceeds to the activation anneal operation 665, which is in theexemplary embodiment to activate the source/drain dopants implanted atoperation 660. At operation 543, a pulsed laser anneal is performed tomelt a top layer(s) of the deposited semiconductor stack without meltingall layers of the stack (e.g., without melting a bottom semiconductorlayer), as described for method 701.

In FIG. 7C, the method 703 begins with depositing a semiconductormaterial stack on a fin to form the raised source/drain at operation415B, as described for method 701. In the exemplary embodiment, themethod 703 proceeds to the activation anneal operation 665. Theactivation anneal is performed to electrically activate any in-situdeposited dopants within the raised source/drain region. However,depending on the deposition process at operation 415B, the in-situdeposited dopants may already be electrically activated in which casethe activation anneal 665 is not employed. At operation 667, asupplemental implant is performed to further enhance dopantconcentration and/or implant a second species distinct from at least oneof the in-situ deposited species. At operation 543, a pulsed laseranneal is performed to melt a top layer(s) of the depositedsemiconductor stack without melting all layers of the stack (e.g.,without melting a bottom semiconductor layer), as described for method701.

FIG. 8 illustrates a computing device 1000 in accordance with oneimplementation of the invention. The computing device 1000 houses aboard 1002. The board 1002 may include a number of components, includingbut not limited to a processor 1004 and at least one communication chip1006. The processor 1004 is physically and electrically coupled to theboard 1002. In some implementations the at least one communication chip1006 is also physically and electrically coupled to the board 1002. Infurther implementations, the communication chip 1006 is part of theprocessor 1004.

Depending on its applications, computing device 1000 may include othercomponents that may or may not be physically and electrically coupled tothe board 1002. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 1006 enables wireless communications for thetransfer of data to and from the computing device 1000. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 1006 may implementany of a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 1000 may include a plurality ofcommunication chips 1006. For instance, a first communication chip 1006may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 1006 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 1004 of the computing device 1000 includes an integratedcircuit die packaged within the processor 1004. In some implementationsof the invention, the integrated circuit die of the processor includesone or more devices, such as non-planar transistors that are formed withpartial melts of the raised source/drain. The term “processor” may referto any device or portion of a device that processes electronic data fromregisters and/or memory to transform that electronic data into otherelectronic data that may be stored in registers and/or memory.

The communication chip 1006 also includes an integrated circuit diepackaged within the communication chip 1006. In accordance with anotherimplementation of the invention, the integrated circuit die of thecommunication chip includes one or more devices, such as non-planartransistors that are formed with partial melts of the raisedsource/drain.

In further implementations, another component housed within thecomputing device 1000 may contain an integrated circuit die thatincludes one or more devices, such as non-planar transistors that areformed with partial melts of the raised source/drain.

In various implementations, the computing device 1000 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 1000 may be any other electronic device that processes data.

The above description is illustrative, and not restrictive. For example,while flow diagrams in the figures show a particular order of operationsperformed by certain embodiments of the invention, it should beunderstood that such order may not be required (e.g., alternativeembodiments may perform the operations in a different order, combinecertain operations, overlap certain operations, etc.). Furthermore, manyother embodiments will be apparent to those of skill in the art uponreading and understanding the above description. Although the presentinvention has been described with reference to specific exemplaryembodiments, it will be recognized that the invention is not limited tothe embodiments described, but can be practiced with modification andalteration within the spirit and scope of the appended claims. The scopeof the invention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

What is claimed is:
 1. A transistor, comprising: a semiconductorsubstrate including a channel region disposed below a gate stack; andsemiconductor source/drain regions coupled to the channel region anddisposed on opposite ends of the channel region with the gate stackdisposed there between, wherein the semiconductor source/drain regionscomprise a super-activated dopant region above a melt depth and anactivated dopant region below the melt depth, the super-activated dopantregion having a higher activated dopant concentration than the activateddopant region, wherein the melt depth is substantially the same alongthe entirety of the semiconductor source/drain regions, and wherein thehigher activated dopant concentration is a constant over thesuper-activated dopant region while the activated dopant concentrationis not a constant over activated dopant region.
 2. The transistor ofclaim 1, wherein the melt depth does not contact the semiconductorsubstrate.
 3. The transistor of claim 1, wherein the super activateddopant region is formed from a first semiconductor material and theactivated dopant region is formed from a second semiconductor materialwherein the first semiconductor material is different from the secondsemiconductor material.
 4. The transistor of claim 3, wherein the firstsemiconductor material has a lower melting point than that of the secondsemiconductor material.
 5. A transistor comprising: a semiconductorsubstrate including a channel region disposed below a gate stack; andsemiconductor source/drain regions coupled to the channel region anddisposed on opposite sides of the channel region with the gate stackdisposed there between, wherein the semiconductor source/drain regionscomprise a first semiconductor material disposed on a secondsemiconductor material wherein the first semiconductor material has alower melting point than that of the second semiconductor material,wherein the first semiconductor material has a material depth, andwherein the first semiconductor material depth is substantially the samealong the entirety of the semiconductor source/drain regions.
 6. Thetransistor of claim 5, wherein the first semiconductor material has ahigher activated dopant concentration than the second semiconductormaterial.
 7. The transistor claim 5, wherein the semiconductor substrateis formed from a third semiconductor material wherein the thirdsemiconductor material is different than the second semiconductormaterial.
 8. The transistor claim 5, wherein the first semiconductormaterial and the second semiconductor material are formed above thechannel region.
 9. The transistor claim 5, wherein the secondsemiconductor material is formed directly adjacent to the channelregion.
 10. A transistor comprising: a semiconductor substrate includinga channel region disposed below a gate stack, the semiconductorsubstrate formed from a first semiconductor material; recesses formed inthe substrate on opposite sides of the channel; and semiconductorsource/drain regions disposed on the recesses and coupled to the channelregion, the semiconductor source/drain regions formed from a secondsemiconductor material, the second semiconductor material different thanthe first semiconductor material, the semiconductor source/drain regionscomprise a super activated dopant region above a melt depth and anactivated dopant region below the melt depth, the super activated dopantregion having a higher activated dopant concentration than the activateddopant region, wherein the melt depth is substantially the same alongthe entirety of the semiconductor source/drain regions, and wherein thehigher activated dopant concentration is a constant over thesuper-activated dopant region while the activated dopant concentrationis not a constant over activated dopant region.
 11. The transistor ofclaim 10, wherein the melt depth does not contact the semiconductorsubstrate.
 12. The transistor of claim 10, wherein the super activateddopant region is formed from a third semiconductor material and theactivated dopant region is formed from the second semiconductor materialwherein the third semiconductor material is different from the secondsemiconductor material.
 13. The transistor of claim 12, wherein thethird semiconductor material has a lower melting point than that of thesecond semiconductor material.
 14. A transistor, comprising: asemiconductor substrate including a channel region disposed below a gatestack; and semiconductor source/drains source/drain regions coupled tothe channel region and disposed on opposite ends of the channel regionwith the gate stack disposed there between, wherein the semiconductorsource/drains source/drain regions comprise a super-activated dopantregion above a melt depth and an activated dopant region below the meltdepth, the super-activated dopant region having a higher activateddopant concentration than the activated dopant region, wherein the meltdepth is substantially the same along the entirety of the semiconductorsource/drain regions, wherein the super activated dopant region isformed from a first semiconductor material and the activated dopantregion is formed from a second semiconductor material wherein the firstsemiconductor material is different from the second semiconductormaterial, and wherein the first semiconductor material has a lowermelting point than that of the second semiconductor material.
 15. Thetransistor of claim 14, wherein the melt depth does not contact thesemiconductor substrate.
 16. The transistor of claim 14, wherein thefirst semiconductor material is GaAs, and the second semiconductormaterial is silicon.
 17. The transistor of claim 14, wherein the firstsemiconductor material is InP, and the second semiconductor material isGaP.
 18. A transistor comprising: a semiconductor substrate including achannel region disposed below a gate stack, the semiconductor substrateformed from a first semiconductor material; recesses formed in thesubstrate on opposite sides of the channel; and semiconductorsource/drain regions disposed on the recesses and coupled to the channelregion, the semiconductor source/drain regions formed from a secondsemiconductor material, the second semiconductor material different thanthe first semiconductor material, the semiconductor source/drain regionscomprise a super activated dopant region above a melt depth and anactivated dopant region below the melt depth, the super activated dopantregion having a higher activated dopant concentration than the activateddopant region, wherein the melt depth is substantially the same alongthe entirety of the semiconductor source/drain regions, wherein thesuper activated dopant region is formed from a third semiconductormaterial and the activated dopant region is formed from the secondsemiconductor material wherein the third semiconductor material isdifferent from the second semiconductor material, and wherein the thirdsemiconductor material has a lower melting point than that of the secondsemiconductor material.
 19. The transistor of claim 18, wherein the meltdepth does not contact the semiconductor substrate.
 20. The transistorof claim 18, wherein the third semiconductor material is GaAs, and thesecond semiconductor material is silicon.